Photophysical Properties and Photovoltaic Performance of Sensitizers with a Bipyrimidine Acceptor

Molecular engineering is a crucial strategy for improving the photovoltaic performance of dye-sensitized solar cells(DSSCs). Despite the common use of the donor-π bridge-acceptor architecture in designing sensitizers, the underlying structure-performance relationship remains not fully understood. In this study, we synthesized and characterized three sensitizers: MOTP-Pyc, MOS_(2)P-Pyc, and MOTS_(2)P-Pyc, all featuring a bipyrimidine acceptor. Absorption spectra, cyclic voltammetry, and transient photoluminescence spectra reveal a photo-induced electron transfer(PET) process in the excited sensitizers. Electron spin resonance spectroscopy confirmed the presence of charge-separated states. The varying donor and π-bridge structures among the three sensitizers led to differences in their conjugation effect, influencing light absorption abilities and PET processes and ultimately impacting the photovoltaic performance. Among the synthesized sensitizers, MOTP-Pyc demonstrated a DSSC efficiency of 3.04%. Introducing an additional thienothiophene block into the π-bridge improved the DSSC efficiency to 4.47% for MOTS_(2)P-Pyc. Conversely, replacing the phenyl group with a thienothiophene block reduced DSSC efficiency to 2.14% for MOS_(2)P-Pyc. Given the proton-accepting ability of the bipyrimidine module, we treated the dye-sensitized TiO_(2) photoanodes with hydroiodic acid(HI), significantly broadening the light absorption range. This treatment greatly enhanced the short-circuit current density of DSSCs owing to the enhanced electron-withdrawing ability of the acceptor. Consequently, the HI-treated MOTS_(2)P-Pyc-based DSSCs achieved the highest power conversion efficiency of 7.12%, comparable to that of the N719 dye at 7.09%. This work reveals the positive role of bipyrimidine in the design of organic sensitizers for DSSC applications.

Photophysical Properties of Rare Earth Complexes with 3,4-Furandicarboxylic Acid and 1,10-Phenanthroline

Synthesis, IR spectra, UV vis spectra and photophysical properties of Gd 3+ , Eu 3+ , Tb 3+ complexes with 3,4 furandicarboxylic acid and 1,10 phenanthroline are reported. Intramolecular energy transfer process for these complexes is discussed in detail. It is found that the intramolecular energy transfer efficiency depends on the relative positions between the resonance energy levels of the central rare earth ions and the lowest triplet state energies of ligands.

Synthesis and Photophysical Properties of Dy^(3+) and Gd^(3+) Polymeric Complexes with Functionalized Polybenzimidazole Containing β-Diketone Side Group

The polymeric ligand PBIa （functionalized polybenzimidazole containing β-diketone side group） was successfully synthesized via the reaction of polybenzimidazole （PBI） with 3-Br-acetylacetone in DM SO solvent using Nail as the deprotonation reagent. Its corresponding polymeric complexes of Dy^3＋ and Gd^3＋ were prepared and characterized by FT-IR, ^1H NMR, molar conductance measurements, and thermal analysis. The photoluminescence properties and the probable mechanism of the Dy and Gd complexes were studied. The measurement and analysis of the thermal properties showed that these were thermal stable.

Synthesis and photophysical properties of metal anthraquinone phthalocyanine

A novel anthraquinone phthalocyanine AI（Ⅲ） 4 and Co（Ⅱ） 5 were synthesized and characterized by elemental analysis, IR UV/ vis, ^1H NMlL HPLC and MS. The photophysical properties of the two metal complexes were studied and compared by fluorescence spectrum method.

Photophysical Property of Ternary Complex Eu(DPHA)_3·Phen·2H_2O

One ternary complex of europium with the plant growth regulator HDPHA (2-Hydroxydiphenyl acetic acid) and Phen (1,10-Phenanthroline), Eu(DPHA) 3·Phen·2H 2O, was synthesized and characterized by the elemental analysis and DTA-TG measurement. The photophysical property of the complex was investigated by means of IR spectra, Raman spectrum and laser-exited, high-resolved excitation and emission spectra as well as time-resolved luminescence spectra. The luminescence spectra reveal four Eu 3+ sites with energy difference within 25 cm -1 and local symmetries of C 1 or C 2 or C s in the complex. The energy transfer among the Eu 3+ sites is observed. The 7F J sublevel splitting of the Eu 3+ ion is discussed.

Regulation of Excited-State Intramolecular Proton Transfer Process and Photophysical Properties for Benzoxazole Isothiocyanate Fluorescent Dyes by Changing Atomic Electronegativity

Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties.Therefore,we selected a series of benzoxazole isothiocyanate fluorescent dyes(2-HOB,2-HSB,and 2-HSe B)by theoretical methods,and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms.The calculated bond angle,bond length,energy gap,and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSe B.Correspondingly,the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSe B.In addition,the calculated electronic spectrum shows that as the atomic electronegativity decreases,the emission spectrum has a redshift.Therefore,this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.

Synthesis of linear and V-shaped oligo(phenylene ethynylene) derivatives:Geometric effects on photophysical properties

A series of linear and V-shaped oligo(phenylene ethynylene) derivatives 1-3 were synthesized through sequent Sonogashira coupling and propargyl alcohol deprotection reaction in high yields.The alkoxy chains(i.e.,n-hexyloxy groups) were introduced to assure good solubility of compounds 1-3 in common solvents.The photophysical properties of 1-3 in solution depend strongly on the geometries of these compounds.

PHOTOPHYSICAL PROPERTIES OF THE ASYMMETRIC PENTAAZADENTATE PORPHYRIN-LIKE MACROCYCLES

The porphyrin-like macrocycles and their metal complexes are s novel family of photoresponsive molecules.The properties of the excited states,both singlet and triplet are investigated by the stationary and transient processes.

Synthesis and Effect of Cation Binding on Photophysical Properties of 1,8-Anthraceno-18-Crown-5

A new type of anthracene crown ether 1, 8-anthraceno-18-crown-5 has been synthesizedand the photophysical properties upon complexation with alkali and alkaline-earth metal canonswere investigated. The fiuorescence quantum yield and lifetime are appreciably enhanced, and thestability constant Ks were determined by fluorometric titration. It was found that the magnitude ofKs is controlled by the size and charge density of the complexed canons.

PHOTOPHYSICAL BEHAVI0RS OF OLIGOMER BASED ON 1, 1′-BINAPHTHOL WITH 3, 3′-ACETYLENE SPACER

The photophysical behaviors of the oligomer based on 1,1'-binaphthol with3,3'-acetylene spacer were investigated. The oligomer molecule has a naphthyl-acetylene-naphthyl effective conjugation segment. The atropic of the 1,1'-binaphthyl moiety led totwisted and rigid main chain in the oligomer. With the changes of the external environ-ment such as solvents used, solvent viscosity and ambient temperature, the wavelengthsof absorption and the intensities of fluorescence and absorption are changed slightly, butthe fluorescent intensity and quantum yield can be influenced. The luminescent behav-iors of the oligomer exhibit twisted intramolecular charge transfer characteristics, whichcould have a potential application in wavelength-stable light emitting material adaptableto ambient temperature and the solvents used in wide range.

Electrochemical, Photophysical, and Magnetic Properties of Green Emitting bis(2,5-Hexyloxy)-Phenylene-<i>alt</i>-Thiophene Fluorescent Conducting Oligomer Addended Fullerene-Diol Dyad

Towards the development of potential new organic photovoltaic and optoelectronic materials, a simple route to synthesize flexibly ether linked fullerene-bis[oligo-(phenylene-alt-thiophene)] and evaluation of electrochemical, photophysical and magnetic properties is presented. Flexible ether linking of oligo-phenylene-thiophene chain to 1, 2 C60(OH)2 is achieved employing Williamson’s ether synthesis. 7-chain phenylene-thiophene chain fluorescent conducting oligomer is synthesized using Grignard coupling reaction with preservation of bromo end groups. Oligomer is highly ordered and soluble in all organic solvents while on linking to fullerene-diol, solubility of adduct restricts only to dimethyl sulfoxide (DMSO). All the synthesized materials are characterized through spectroscopic techniques and molecular weight is determined by mass spectrometry and GPC. Properties of the material indicate the substantial effect of fullerene. High quenching in fluorescence intensity and strong paramagnetic property are observed in this material.

Synthesis and Photophysical Properties of Fluorene or Carbazole-Based Alternating Copolymers Containing Si and Ethynylene Units in the Main Chain

Alternating copolymerization of 9,9-dihexyl-2,7-dibromofluorene, N-hexyl-2,7-dibromocarbazole (HCz) with diethynyldimethylsilane, diethynyldiphenylsilane, has been investigated using Sonogashira coupling reaction. Photophysical properties of the resulting copolymers were investigated with UV-Vis absorption and photoluminescence spectroscopy. All the copolymers in chloro-form solution showed absorption peaks at 270 - 280 nm with shoulder peaks at around 380 nm derived from π-π* transition or intra-molecular charge transfer through σ-π moiety, respectively. The chloroform solutions of the copolymers showed broad emission peaks at 415 - 425 nm. The emission wave lengths of the copolymers in the solid state (cast film) detected at 360 - 385 nm were remarkably blue-shifted in comparison with those in the chloroform solutions. Hydrosilylation reaction of the copolymers with 1,4-bis(dimethylsilyl)benzene yielded networked copolymers soluble in chloroform, indicating formation of branching polymers. The chloroform solutions of the HCz-based networked copolymers showed bimodal emission derived from new highly energy states in the σ-π conjugation.

Synthesis,Crystal Structure,Photophysical and Redox Properties of a Novel Ru(Ⅱ) Complex with Carbazole-grafted 2-(2-Pyridyl)benzimidazole

A novel Ru（Ⅱ） complex [（bpy）2Ru（PBC）]（PF6）2 （PBC = N-[4-（9-carbazole）butyl]-2-（2-pyridyl）benzimidazole） has been synthesized and verified by 1↑H NMR, elemental analysis and X-ray crystallography. The crystal （C48H40F12N8P2Ru, Mr = 1119.89） belongs to the triclinic system, space group P1, with a = 13.128（4）, b = 13.814（4）, c = 14.184（4） A, α = 84.112（6）, β = 88.473（6）, γ = 78.196（6）°, Z = 2, V = 2504.6（13）A^3, Dc = 1.485 g/cm^3, F（000） = 1132, R = 0.0750 and wR = 0.1896. The Ru atom adopts a distorted-octahedral coordination geometry with the bond distances and bond angles falling in normal ranges. The complex shows an intense metal-to-ligand charge transfer （1MLCT） （dπ（Ru） →π＊（L）） transition （ε ~1.2×10^4 dm^3mol^-1cm^-1） at 457 nm in the UV-Vis absorption spectrum and a strong red phosphorescence at 632 nm in the CH3CN solution at ambient temperature. An efficient intramolecular energy transfer process from the carbazole unit to the [（bpy）2Ru（PB）]^2＋ emissive center exists by selective optical-simulation. Its electrochemical behavior shows multiplicate redox processes based on the metal center, the grafting carbazole moiety and the 2-（2-pyridyl）benzimidazole unit.

PHOTOPHYSICAL STUDY OF SULFONATED POLYSTYRENE

The photophysical properties of a series of sulfonated micromolecule (paratoluenesulfonic acid, HPTS) and macromolecules (linear and crosslinked polystyrene) have been studied by steady-state fluorescence spectra. The results indicate that the ground sulfonated ring associations can form in both the micromolecules and the macromolecules. The fluorescence spectra of the sulfonated crosslinked copolymers appear a red-shift when the copolymers change from hydrogen-type to sodium-type, and some new emission bands appear in the long-wavelength region. These results are explained in terms of synergetic effect of hydrogen bond,π-πinteraction and crosslinking effect.

Construction of metallo-complexes with 2,2′:6′,2″-terpyridine substituted triphenylamine in different modified positions and their photophysical properties

The stable coordinated metallo-complexes based on 2,2′:6′,2″-terpyridine(tpy)and its derivatives have been widely researched for various wide-ranging applications in photoelectronics,catalysis,sensor,photoluminescence,and so on.However,the most reported studies ignored the comprehensive comparison between structures modified by different positions and photoluminescence.Herein,we design a series of metallo-complexes which were assembled with tpy substituted triphenylamine(TPA)at different positions and metal ions and explored their photophysical properties.In the solution state,MLE_(2)based on the 5,5″-positions modification showed the highest PLQYs and PL intensity.With the increase of solvent polarity,MLB2exhibit the largest redshift.In the solid state,from MLA_(2)to MLE_(2),the emission colours are gradually red-shifted from yellow to red.The findings in this work may pave a new way to design functional metallo-complexes,not just for PL properties.

Tailor-Made Dynamic Fluorophores:Precise Structures Controlling the Photophysical Properties

Organic fluorophores with dynamic conformations in the excited state have played a significant role in applications of organic functional dyes.Among them,dihydrophenazine-based dynamic fluorophores involving a photoinduced structural planarization process in the excited state exhibited large Stokes shifts and conformation-dependent multicolor emissions.With the developments of synthetic strategies,precise modifications on dihydrophenazinebased scaffolds have successfully afforded a variety of precise molecular structures of varying sizes and compositions,which have delicately modulated their photophysical properties.Herein,this Perspective summarizes the precise modulations of dihydrophenazine-based dynamic fluorophores,including the development of the synthetic methodologies,and tailor-made molecular models to reveal the luminescence−structure relationships.

Synthesis, Photophysical Properties and Near Infrared Electroluminescence of 1 （4）,8（11）,15（18）,22（25）-Tetra- （methoxy-phenoxy） phthalocyanine

A new soluble phthalocyaine 1 （4）,8（11）, 15（18）,22（25）-tetra-（methoxy-phenoxy）phthalocyanine （MPPc） was synthesized and verified by mass spectrum （MS）, 1H NMR, IR and elemental analysis. The methoxy-phenoxy groups were introduced in order to enhance the solubility of the phthalocyanine. The photophysical and electrolu- minescent properties were investigated. The organic light-emitting diodes （OLEDs） with the structure of ITO/PVK：MPPc（40 nm）/BCP（20 nm）/Alq3（30 nm）/Al were fabricated. Room-temperature near infrared （NIR） electroluminescence （EL） was observed near 891 nm that effectively covered the first optical communication win- dow near 850 nm.

Hydrothermal Preparation and Photophysical Properties of a Ni(Ⅱ) Complex Containing Quinoline Derivative and Phen Ligands

A novel nickel complex[Ni_(2)L_(2)Phen_(3)]·3H_(2)O (HL=3-hydroxy-2-methylquioline-4-carboxylic acid)has been synthesized by a hydrothermal approach and is structurally determined by single-crystal X-ray diffraction.The title complex crystallizes in triclinic space group P1.Crystal data for the title complex:C58H44N8Ni2O9,Mr=1108.35,a=11.8648(4),b=12.7369(4),c=17.0728(5)A,α=97.694(3),β=96.702(2),γ=99.566(3)°,V=2495.66(14)A^(3),Z=2,T=293(2) K,Dc=1.475 g/cm^(3),μ(Mo Kα)=0.824 mm^(–1),F(000)=1140,R=0.0757,w R=0.2129 and GOF=1.017.The nickel ions are surrounded by five oxygen and six nitrogen atoms to yield two slightly distorted octahedral geometries.Solid-state photoluminescence spectrum reveals that it shows blue purple emission.Solid-state UV/Vis diffuse reflectance spectroscopy exhibits that it has an optical band gap of 1.702 e V.

Synthesis and photophysical properties of linear and hy-perbranched conjugated polymer

A novel light-emitting alternating copolymer, known as hyperbranched conjugated polymer (HPV), has been designed and synthesized by Wittig reaction, and so have its linear counterparts, including MPV and PPV. FTIR, 1H NMR, 13C NMR and GPC were combined to characterize these polymers. Their photophysical properties were investigated both in solution and in solid film. Interestingly, almost the same maxima of absorption and emission wavelengths were observed for the solution of HPV and MPV in CH2Cl2 respectively, located at the shorter wavelength region related to PPV. In addition, the absorption peak of HPV film blue shifted while its emission peak red shifted as MPV compared with the case of its CH2Cl2 solution. However, both the absorption and emission spectra of the PPV film showed red shift, which resulted from a special electronic structure.

Synthesis of New Ruthenium(II) Bipyridyl Complexes and Studies on Their Photophysical and Photoelectrochemical Properties

Two new mixed ligand ruthenium(II) complexes, Ru(dcbpy)^(LL)(NCS) 2 [where dcbpy=4,4′ dicarboxyl 2,2′ bipyridine, LL=4,4′ bis( N methyl anilinomethyl) 2,2′ bipyridine (1) or 4 methyl 4′ N methyl anilinomethyl 2,2′ bipyridine (2)], were synthesized, and the photophysical properties of these complexes were studied. The metal to ligand charge transfer (MLCT) transitions of these complexes exhibited solvatochromic effect due to the existence of NCS ligands. The MLCT energies also strongly depend on the pH values of the solutions because of protonation and deprotonation of the carboxyl groups. The p K a values of the ground state, 4 0 for 1 and 3 8 for 2, were obtained from the titration curves. The photoelectrochemical properties of 1 and 2 as sensitizers in sandwich type solar cells have been studied. Complex 1 exhibited better photoelectrochemical behavior than complex 2 as expected. It was proved that the design of mixed ligand complex by introducing electron donating group in one of the ligands should be a promising approach.